<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>div span</title>
    <style>
        * {margin: 0; padding: 0;}
        .box {
            width: 300px;
            height: 300px;
            background-color: purple;
        }
        span {
            margin-left: 10px;
            background-color: yellow;
        }
    </style>
</head>
<body>
    <!-- 标准文档流, 脱离文档流, BFC 三种不同的布局格式上下文 -->
    <!-- 块元素: 独占一行, width 默认auto, 自上而下排列, 布局页面, 先上下, 后左右摆放盒子 -->
    <!-- 行内元素: 宽度为内容大小, 不独占一行, 一般用来放置文字 -->
    <!-- 行内块元素: imgs iframe -->
    <div class="box"></div>
    <span>this is span</span>
    <span>this is span</span>
    <span>this is span</span>
    <span>this is span</span>
</body>
</html>